Communication System, Network Handover Processing Method and Apparatus

ABSTRACT

A communication system, a network handover processing method and a network handover processing apparatus are disclosed. The method includes receiving, by a target evolution NodeB (T-eNB), identity information sent from a user equipment (UE), the identity information being allocated to the UE by a source evolution NodeB (S-eNB); and sending, by the T-eNB, parameters to the UE if identity information, matching the received identity information sent from the UE, is available in the T-eNB, wherein the parameters are allocated to the UE. The apparatus includes a receiving module and a sending module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/683,824,filed on Jan. 7, 2010 and now U.S. Pat. No. 8,406,194, issued Mar. 26,2013, which is a continuation of International Application NO.PCT/CN2008/072090 filed on Aug. 21, 2008, which claims priority toChinese Patent Application No. 200710076513.0, filed on Aug. 22, 2007,all of which are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a wireless communication technology,and in particular, to a communication system, a network handoverprocessing method and a network handover processing apparatus.

BACKGROUND

In evolved network architecture, the handover of an X2 interface takesplace between Evolved NodeBs (eNodeBs). An eNodeB where a User Equipment(UE) is currently located is called a Source eNodeB (S-eNB). An eNodeBto which the UE is handed over is called a Target eNodeB (T-eNB). Thehandover is a process of handing over the UE from a cell controlled bythe S-eNB to a cell controlled by the T-eNB.

The handover process in the prior art is as follows.

The UE context in the S-eNB includes roaming restriction information.The information is provided at the setup of a connection or the updateof a last Tracking Area (TA).

According to the measurement result of the UE and the Radio ResourceManagement (RRM) of the S-eNB, the S-eNB determines to hand over the UEto a cell controlled by the T-eNB.

The S-eNB sends a handover request message to the T-eNB. The messagecarries mandatory information for the handover preparation on the T-eNB,including: MME UE S1AP ID (identity), old enb UE S1AP ID, target cellID, Radio Resource Control (RRC) context, and System ArchitectureEvolution (SAE) bearer context. The T-eNB addresses the S-eNB and theEvolved Packet Core (EPC) according to MME UE S1AP ID or enb UE S1AP ID.The SAE bearer context includes the mandatory address information of theradio network layer and transport network layer, the Quality of Service(QoS) profile of the SAE bearer, and possible configuration informationof the access layer. The T-eNB is configured with necessary resources.

The T-eNB implements admission control to improve the handover successpossibility according to the received QoS profile of the SAE bearer. Ifthe T-eNB is able to meet the resource requirement of the SAE bearer,the T-eNB allocates appropriate resources according to the received QoSprofile of the SAE bearer and meanwhile, reserves a Cell-Radio NetworkTemporary Identifier (C-RNTI).

The T-eNB sends a handover request ACK message to the S-eNB. The messagecarries the newly allocated C-RNTI and parameters, for example, accessparameters, Radio Network Layer (RNL) and/or Transport Network Layer(TNL) information for setting up a forwarding tunnel.

The UE receives a handover command message sent from the S-eNB.According to the message, the UE implements the handover process. Themessage carries the newly allocated C-RNTI and possible start time.

If the target cell is accessed successfully, the UE sends a handoverconfirm message to the T-eNB, indicating that the handover is complete.The T-eNB checks whether the C-RNTI in the message is allocated byitself.

The T-eNB sends a handover complete message to the EPC, indicating thatthe UE have changed the cell. The EPC hands over the data path to theT-eNB and releases the relevant user plane resources and transportnetwork layer resources of the S-eNB.

The EPC sends a handover complete ACK message to the T-eNB to confirmthat the handover is complete.

The T-eNB sends a release resource message to the S-eNB to trigger theS-eNB to release resources.

Upon reception of the release resource message, the S-eNB releases theradio resources and control plane resources related to the UE context.

In the above handover preparation process, if the radio link between theS-eNB and the UE fails, the UE changes the state during the subsequenthandover. As a result, the handover is delayed and the system resourcesare wasted.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a communication system, anetwork handover processing method and a network handover processingapparatus.

An embodiment of the present invention provides a network handoverprocessing method. A T-eNB receives ID information sent from a UE. TheID information is allocated for the UE by an S-eNB. The T-eNB sendsparameters to the UE if identity information that matches the receivedidentity information sent from the UE is available in the T-eNB. Theparameters are allocated to the UE by the T-eNB. The handover process isthen continued.

A network handover processing apparatus Another embodiment of thepresent invention provides a network handover processing apparatus. Areceiving module is adapted to receive ID information sent from a UE.The ID information is allocated for the UE by an S-eNB. A sending moduleis adapted to send parameters allocated for the UE to the UE if identityinformation, matching the received identity information sent from theUE, is available in the T-eNB.

A communication system provided in an embodiment of the presentinvention includes a UE, an S-eNB and a T-eNB. The UE is adapted todiscover a target cell after detecting a radio link failure and to sendID information allocated for the UE by the S-eNB to the T-eNBcorresponding to the target cell. The T-eNB is adapted to sendparameters allocated for the UE to the UE if the T-eNB has IDinformation the same as the ID information sent from the UE, andcontinue the handover process.

The communication system, network handover processing method and networkhandover processing apparatus in the embodiments of the presentinvention determine whether the T-eNB is the selected T-eNB during thenetwork handover preparation, that is, check whether the contextinformation of the UE exists by judging whether the T-eNB has IDinformation the same as the ID information sent from the UE. If the sameID information exists, the handover process is continued. Thus, thestate change times of the UE in the network handover process arereduced, and the system resources are saved.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 shows a first flowchart of a network handover processing methodaccording to an embodiment of the present invention;

FIG. 2 shows a second flowchart of a network handover processing methodaccording to an embodiment of the present invention;

FIG. 3 shows a structure of a network handover processing apparatusaccording to a first apparatus embodiment of the present invention;

FIG. 4 shows a structure of a network handover processing apparatusaccording to a second apparatus embodiment of the present invention; and

FIG. 5 shows a structure of a communication system according to anembodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The embodiments of the present invention are hereinafter described indetail with reference to the accompanying drawings.

During the handover preparation in an evolved network, if a radio linkfailure occurs between the S-eNB and the UE, the UE detects a cell withbetter signal quality and sends a cell update message to the T-eNBcorresponding to the cell. If the cell previously received a handoverrequest message sent from the UE during the handover preparation and theT-eNB stores the context of the UE, the T-eNB may send the parameterssuch as the air interface resource configuration information, securityparameter, and C-RNTI to the UE through a cell update confirm message orother messages so that the handover process can be continued.

During the handover preparation in an evolved network, if a radio linkfailure occurs between the S-eNB and the UE, the UE detects a cell withbetter signal quality and sends a cell update message to the T-eNBcorresponding to the cell. The ID information allocated by the S-eNB maybe carried in the cell update message or other RRC layer access messagessent to the T-eNB. Alternatively, the cell update cause value may becarried in the cell update message or other RRC layer access messages tothe T-eNB. The T-eNB checks whether identity information, matching thereceived identity information sent from the UE, is available in theT-eNB, if identity information is available in the T-eNB, it indicatesthat the context of the UE does exist in the T-eNB. In this case, theT-eNB delivers the relevant radio parameter information, securityparameter, and C-RNTI to the UE. The handover process is continued. Thespecific process is described below with reference to FIG. 1.

Step 101: The S-eNB sends a handover request message to a candidateT-eNB. One or more candidate T-eNBs may be available. Accordingly, theS-eNB may send a handover request message to one or more candidateT-eNBs. In this embodiment, two candidate T-eNBs are selected, that is,T-eNB1 and T-eNB2.

The handover request message carries the ID information allocated forthe UE by the S-eNB. For example, the ID information may include one orany combination of: C-RNTI, S-TMSI, other ID of UE, source cell ID, andS-eNB ID.

Step 102: If the candidate T-eNBs accept the handover request andrespond with a handover request ACK message, the S-eNB may receivemultiple handover request ACK messages from different candidate T-eNBs.As shown in FIG. 1, the candidate T-eNB1 and T-eNB2 respectively send ahandover request ACK message to the S-eNB. Through the handover requestACK message, the candidate T-eNBs may allocate a new C-RNTI to the UE.The security parameter and radio configuration parameter container mayalso be allocated. The radio configuration parameter container mayinclude the Radio Bearer (RB) and Packet Data Convergence Protocol(PDCP) parameters. This embodiment does not limit the parameters thatcan be allocated by the candidate T-eNBs.

Step 103: The UE detects that the radio link between the UE and theS-eNB fails.

Step 104: The UE finds a target cell with better signal quality andconnects to the cell.

Step 105: The UE sends a cell update message to an eNB corresponding tothe cell, that is, a new T-eNB.

The cell update message carries the ID information allocated by theS-eNB. For example, the ID information may include one or anycombination of: C-RNTI, S-TMSI, other ID of UE, source cell ID, andS-eNB ID.

Further, the cell update message may carry a cell update cause value,for example, “radio link failure.”

Step 106: The new T-eNB judges whether itself is the candidate T-eNBselected in step 101.

Upon reception of the cell update message, the new T-eNB obtains the IDinformation that is allocated for the UE by the S-eNB and carried in themessage, and queries whether identity information, matching the receivedidentity information sent from the UE, is available in the T-eNB. If theidentity information is available in the T-eNB, it indicates that thecontext of the UE does exist in the T-eNB; that is, the new T-eNB is thecandidate T-eNB selected in step 1, and the process goes to step 107. Ifthe identity information isn't available in the T-eNB, the T-eNB sends acell update Failure message to the UE and ending the process. In FIG. 1,the T-eNB selected by the UE is the T-eNB1.

Step 107: The new T-eNB constructs a cell update confirm message andsends the message to the UE. The message carries the parametersallocated for the UE by the T-eNB. The message may carry the securityparameter, C-RNTI parameter, and parameters in the radio configurationparameter container. This embodiment does not limit the parameters thatcan be allocated by the candidate T-eNBs. The condition for keeping thesecurity parameter unchanged is: the UE does not delete the K_(ENB) keyduring the radio link failure; the UE uses the key after receiving thecell update confirm message.

Step 108: The UE returns a mobility complete message to the T-eNB. Themessage includes the configuration information of some confirmed radioparameters, for example, RB.

Step 109: Upon reception of the mobile complete message, the T-eNB sendsa handover complete message to the mobility management Entity (MME).

Step 110: The MME returns a handover complete ACK message to the T-eNB.

Step 111: The T-eNB notifies the S-eNB to release resources and sends arelease resource message to the S-eNB.

Step 112: When multiple candidate T-eNBs are available, the S-eNB sendsa release resource message to other candidate T-eNBs.

In this embodiment, the handover request message that the S-eNB sends tothe candidate T-eNBs carries the ID information allocated for the UE bythe S-eNB. The cell update message that the UE sends after the radiolink between the UE and the S-eNB fails also carries the ID informationallocated for the UE by the S-eNB. The new T-eNB receiving the cellupdate message judges whether identity information, matching thereceived identity information sent from the UE, is available in theT-eNB. If the identity information is available in the T-eNB, the newT-eNB is the candidate T-eNB selected by the UE during the handoverpreparation, and the context of the UE is already stored. Thus, theT-eNB does not need to obtain the context from the S-eNB, and thehandover delay is reduced. The UE can stay in the active state, insteadof changing from the active state to the idle state and then changingback to the active state. Thus the state change times are reduced andthe system resources are saved.

A second embodiment will now be described.

When the S-eNB detects that the radio link with the UE fails, the S-eNBsends a message to a candidate T-eNB through the X2 interface. Themessage carries the ID information allocated for the UE by the S-eNB.The specific process is described below with reference to FIG. 2.

Step 201: The S-eNB sends a handover request message to a candidateT-eNB. One or more candidate T-eNBs may be available. Accordingly, thehandover request message may be sent to one or more candidate T-eNBs. Inthis embodiment, two candidate T-eNBs are selected.

Step 202: If the candidate T-eNBs accept the handover request, thecandidate T-eNBs return a handover request ACK message to the S-eNB. TheS-eNB may receive multiple handover request ACK messages from differentcandidate T-eNBs. As shown in FIG. 2, the candidate T-eNB1 and T-eNB2respectively return a handover request ACK message to the S-eNB.

Through the handover request ACK message, the candidate T-eNBs mayallocate a new C-RNTI to the UE. The security parameter and radioconfiguration parameter container may also be allocated. The radioparameter container may include the RB and PDCP parameters. Thisembodiment does not limit the parameters that can be allocated by thecandidate T-eNBs.

Step 203: The S-eNB detects that the radio link between the UE and theS-eNB fails.

Step 204: The S-eNB sends a message to one or more candidate T-eNBsthrough the X2 interface. For example, the message may be a handovercommit message and the message carries the ID information allocated forthe UE by the S-eNB. For example, the ID information may include one orany combination of: C-RNTI, S-TMSI, other ID of UE, source cell ID, andS-eNB ID.

Steps 205-213 are similar to the corresponding steps in the firstembodiment.

The enumerated messages and the carried parameters in this embodimentare exemplary only. The present invention does not limit the specificforms of the messages or specific forms of the parameters carried in themessages.

An embodiment of the present invention also provides a network handoverprocessing apparatus. As shown in FIG. 3, the apparatus includes areceiving module 1 and a sending module 2. The receiving module 1 isadapted to receive identity information sent from the UE. The IDinformation is allocated to the UE by the S-eNB. The sending module 2 isadapted to send the parameters allocated for the UE to the UE ifidentity information, matching the received identity information sentfrom the UE, is available in the T-eNB, and to continue the handoverprocess.

In this embodiment, the receiving module 1 receives the ID informationallocated for the UE by the S-eNB and queries whether identityinformation, matching the received identity information sent from theUE, is available in the T-eNB. If the identity information is availablein the T-eNB, it indicates that the T-eNB is the candidate T-eNBselected during the handover preparation. The candidate T-eNB has thecontext information of the UE and can perform the network handover. TheT-eNB sends the parameters allocated for the UE to the UE. Theparameters may include the security parameter, C-RNTI, RB, and PDCP. Thenetwork handover processing apparatus provided in this embodiment canreduce the handover delay. The UE can stay in the active state all alongduring the network handover, instead of changing from the active stateto the idle state and then changing back to the active state. Thus thestate change times are reduced and the system resources are saved.

As shown in FIG. 4, based on the foregoing embodiment, the networkhandover processing apparatus may further include an obtaining module inaddition to the receiving module 1 and the sending module 2. Theobtaining module 3 is adapted to obtain the ID information sent throughthe Handover Request message by the S-eNB, or to obtain the IDinformation sent by the S-eNB after the radio link between the UE andthe S-eNB fails.

The ID information received by the receiving module and sent from the UEincludes one or any combination of: C-RNTI, S-TMSI, other ID of UE,source cell ID, and S-eNB ID.

The network handover processing apparatus in this embodiment may be setin a NodeB as a functional module of the NodeB. The apparatus canimplement the process of the foregoing method embodiment.

An embodiment of the present invention provides a communication system.As shown in FIG. 5, the system includes a UE 4, an S-eNB 5, and a T-eNB6. The UE 4 is adapted to discover a target cell after detecting a radiolink failure and to send the ID information allocated for the UE 4 bythe S-eNB 5 to a T-eNB 6 corresponding to the target cell. The T-eNB 6is adapted to send parameters allocated for the UE 4 to the UE 4 if theT-eNB 6 has ID information the same as the ID information sent from theUE 4, and to continue the handover process.

In the communication system provided by this embodiment, after the radiolink failure occurs during the network handover, the UE sends the IDinformation to the selected T-eNB. By judging whether the T-eNB has thesame ID information, the T-eNB can know whether the T-eNB is thecandidate T-eNB selected by the S-eNB during the network handoverpreparation, that is, whether the context information of the UE exists.If the same ID information exists, the handover process is continued.Thus the state change times are reduced and the handover efficiency isimproved. The UE can stay in the active state, instead of changing fromthe active state to the idle state and then changing back to the activestate. Thus the state change times are reduced and the system resourcesare saved.

The ID information in the T-eNB in this embodiment is sent by the S-eNB.The S-eNB may send the ID information to the T-eNB through a HandoverRequest message. Alternatively, when the radio link with the UE fails,the S-eNB may send the ID information to the T-eNB.

The T-eNB is further adapted to send the radio bearer configurationparameters to the UE and to continue the handover process. The S-eNB isadapted to send the ID information allocated for the UE to at least onecandidate T-eNB.

The communication system provided in this embodiment can enable the UEto stay in the active state all along during the network handover,instead of changing from the active state to the idle state and thenchanging back to the active state. Thus the state change times arereduced and the system resources are saved.

In the foregoing embodiments, the S-eNB allocates the ID information tothe UE and sends the ID information to the candidate T-eNB; when a radiolink failure occurs, the UE sends the ID information to the T-eNB; ifthe T-eNB has the same ID information, it indicates that the T-eNB isone of the candidate T-eNBs and stores the context information of theUE. Hence, the T-eNB does not need to obtain the context from the S-eNB.Therefore, the handover delay is reduced, and the UE can stay in theactive state, instead of changing from the active state to the idlestate and then changing back to the active state. Thus the state changetimes are reduced and the system resources are saved.

Although the technical solution of the present invention has beendescribed through exemplary embodiments, the invention is not limited tosuch embodiments. It is apparent that those skilled in the art can makevarious modifications and variations to the invention without departingfrom the spirit and scope of the invention. The invention is intended tocover the modifications and variations provided that they fall in thescope of protection defined by the claims or their equivalents.

What is claimed is:
 1. A method for performing a network handoverprocess, the method comprising: receiving from a source evolved NodeB(eNB), by a target eNB, first identity information allocated to a userequipment by the source eNB; receiving, by the target eNB, secondidentity information allocated to the user equipment by the source eNBsent from the user equipment, wherein the second identity information issent after a radio link failure is detected by the user equipment;determining, by the target eNB, whether the second identity informationmatches the first identity information; and when the second identityinformation matches the first identity information, sending, by thetarget eNB, one or more parameters to the user equipment, wherein theone or more parameters are allocated to the user equipment by the targeteNB; wherein the first identity information and the second identityinformation each comprise a Cell Radio Network Temporary Identifier(C-RNTI) and a source cell identity.
 2. The method according to claim 1,further comprising receiving, by the target eNB, a cause value sent fromthe user equipment together with the second identity information.
 3. Themethod according to claim 1, further comprising storing, by the targeteNB, the first identity information.
 4. The method according to claim 1,wherein receiving the first identity information comprises receiving, bythe target eNB, a handover request message sent from the source eNB,wherein the handover request message comprises the first identityinformation allocated to the user equipment by the source eNB.
 5. Themethod according to claim 1, further comprising ending the handoverprocess when the second identity information does not match the firstidentity information.
 6. The method according to claim 1, furthercomprising: receiving, by the target eNB, a mobility complete messageresponded by the user equipment; sending, by the target eNB, a handovercomplete message to a mobility management entity upon reception of themobile complete message; receiving, by the target eNB, a handovercomplete ACK message from the mobility management entity; and sending,by the target eNB, a first release resource message to the source eNB,thereby enabling the source eNB to release resources.
 7. The methodaccording to claim 6, further comprising, when multiple candidate targeteNBs are available, sending, by the target eNB, a second releaseresource message to other candidate target eNB(s) of the multiplecandidate target eNBs upon the reception of the first release resourcemessage.
 8. An evolved NodeB (eNB) in a communication network that is atarget eNB in a handover process, the eNB comprising: a communicationinterface, configured to receive from a source eNB, first identityinformation allocated to a user equipment by the source eNB; a receiver,configured to receive second identity information allocated to the userequipment by the source eNB sent from the user equipment, wherein thesecond identity information is sent after a radio link failure isdetected by the user equipment; a processor, configured to determinewhether the second identity information matches the first identityinformation and to allocate one or more parameters to the user equipmentwhen the second identity information matches the first identityinformation, wherein the first identity information and the secondidentity information each comprises a Cell Radio Network TemporaryIdentifier (C-RNTI) and a source cell identity; and a transmitter,configured to send the one or more parameters to the user equipment. 9.The eNB according to claim 8, wherein the receiver is further configuredto receive a cause value sent from the user equipment together with thesecond identity information.
 10. The eNB according to claim 8, furthercomprising a storage unit, configured to store the first identityinformation received from the source eNB.
 11. The eNB according to claim8, wherein the communication interface is configured to receive ahandover request message, sent from the source eNB, wherein the handoverrequest message includes the first identity information allocated to theuser equipment by the source eNB.
 12. The eNB according to claim 8,wherein the receiver is further configured to receive a mobilitycomplete message responded by the user equipment; the transmitter isfurther configured to send a handover complete message to a mobilitymanagement entity upon reception of the mobile complete message; thereceiver is further configured to receive a handover complete ACKmessage from the mobility management entity; and the transmitter isfurther configured to send a first release resource message to thesource eNB, thereby enabling the source eNB to release resources. 13.The eNB according to claim 8, wherein the transmitter is furtherconfigured to send a second release resource message to anothercandidate target eNB upon reception of the first release resourcemessage.
 14. A method for performing a network handover process, themethod comprising: determining, by a user equipment, a target cell afterdetecting a radio link failure; sending, by the user equipment, secondidentity information to a target evolved NodeB (eNB) corresponding tothe target cell, wherein the second identity information is allocated tothe user equipment by a source eNB; and receiving, by the userequipment, one or more parameters allocated by the target eNB, sent fromthe target eNB; wherein the one or more parameters are sent from thetarget eNB when the target eNB determines that the second identityinformation matches first identity information received from the sourceeNB; and wherein the first identity information and the second identityinformation each comprises a Cell Radio Network Temporary Identifier(C-RNTI) and a source cell identity.
 15. The method according to claim14, further comprising sending, by the user equipment, a cause value tothe target eNB together with the second identity information.
 16. Themethod according to claim 14, wherein the first identity informationallocated to the user equipment which is sent to the target eNB by thesource eNB is stored in the target eNB.
 17. A user equipment configuredto be in communication with a plurality of evolved NodeBs (eNBs) in ahandover process, wherein at least one of the eNBs is a source eNB andat least one of the eNBs is a target eNB, the user equipment comprising:a processor, configured to determine a target cell after detecting aradio link failure; a transmitter, configured to send second identityinformation to the target eNB corresponding to the target cell, whereinthe second identity information is allocated to the user equipment bythe source eNB; and a receiver, configured to receive one or moreparameters allocated by the target eNB and sent from the target eNB;wherein the one or more parameters are sent from the target eNB when thetarget eNB determines that the second identity information matches firstidentity information received from the source eNB; and wherein the firstidentity information and the second identity information each comprisesa Cell Radio Network Temporary Identifier (C-RNTI) and a source cellidentity.
 18. The user equipment according to claim 17, wherein thetransmitter is further configured to send a cause value to the targeteNB together with the second identity information.
 19. The userequipment according to claim 17, wherein the first identity informationallocated to the user equipment which is sent to the target eNB by thesource eNB is stored in the target eNB.